Automatically focusing field emission electrode

Abstract

Several embodiments of a thin film field emission cathode array are described which automatically shape the beams of emitted particles, without the addition of shaping or other electrode structure. A potential field pattern is established to control the trajectory of the emitted particles, by controlling the electromagnetic interaction of the conductive structures responsible for the particle emission.

I claim: 
     
       1. A particle field emission structure comprising, in combination: at least one particle emission site having one or more emitting tips for electrically charged particles; an electrically conductive base structure positioned to provide electrical energy to said emitting tips for electrically charged particles to be emitted therefrom; an electrically conductive control electrode structure positioned at said site for controlling the extraction of particles from said site; means for applying a potential difference between said base structure and said control electrode to extract electrically charged particles from said particle emission site; said control electrode, base structure, and potential applying means being selected to have an electromagnetic interaction between said control electrode and said base structure providing both an extraction potential for said particles and automatically establishing a potential field pattern in the spatial volume adjacent said control electrode structure on the side thereof opposite said base structure which will provide desired trajectories therethrough of particles formed at said site. 
     
     
       2. The particle field emission structure of claim 1 wherein said electrically conductive base structure is integral with said emission site, and said one or more electrically charged particle emitting tips project from said base structure. 
     
     
       3. The particle field emission structure of claim 1 wherein said tips are electron emitting tips and said particles to be extracted therefrom are electrons. 
     
     
       4. The particle field emission structure of claim 1 wherein said potential difference between said base structure and control electrode is varied relative to the spatial location of said electrodes to one another. 
     
     
       5. The particle field emission structure of claim 1 wherein there are a plurality of said particle emission sites spaced apart from one another and said control electrode and base structures have geometrical shapes between said sites which are related to one another so as to establish said potential field pattern. 
     
     
       6. The particle field emission structure of claim 5 wherein said potential difference between said base structure and control electrode is varied relative to the spatial location of said electrodes to one another. 
     
     
       7. The particle field emission structure of claim 5 wherein said geometrical shapes are selected to have a relationship to direct particles emitted from said sites into said volume, into generally non-diverging beams. 
     
     
       8. The particle field emission structure of claim 6 wherein said electrically conductive base has a generally continuous and planar surface between said emission sites and the electrode structure includes generally annular sections for said sites, each of which circumscribes an associated one of said sites, and a generally linear conduction sections extending between adjacent annular sections, the region between adjacent emission sites otherwise being free of control electrode structure whereby potential on said control structure generally does not interfere with potential on said base defining said potential field pattern in said region. 
     
     
       9. The particle field emission structure of any of the previous claims, further including an electrical insulator structure at each of said sites between said electrically conductive base and said control electrode structure. 
     
     
       10. A method of generating electrically charged particles and controlling the initial trajectory thereof, comprising the steps of: A. Providing at least one particle emission site having one or more electrically charged particle emitting tips;   B. Providing an electrically conductive base structure positioned to provide electrical energy to said emitting tips for electrically charged particles to be emitted therefrom;   C. Providing an electrically conductive control electrode structure at said site for controlling the extraction of particles from the emitting tips thereat; and   D. Controlling a potential difference between said base structure and said control electrode to extract electrically charged particles from said particle emission site and to automatically establish a potential field pattern which will interact with electrically charged particles in the spatial volume adjacent said control electrode structure on the side thereof opposite said base by selecting a desired electromagnetic interaction between said base and control electrode structures during the extraction of particles from said site.   
     
     
       11. The method of claim 10 wherein said step of controlling the potential field pattern which will interact with charged particles produced at each of said sites includes providing a preselected geometrical relationship between said base structure and said control electrode structure adjacent said site. 
     
     
       12. The method of claim 11 wherein said step of controlling the potential field pattern which will interact with charged particles produced at each of said sites includes distributing the potential differences between said base structure and said control electrode structure. 
     
     
       13. The method of claim 10 wherein said steps of providing at least one charged particle emission site and providing an electrically conductive base structure comprises the step of providing an electrically conductive base structure having one or more electrically charged particle emission tips extending integrally therefrom to define said emission site. 
     
     
       14. The method of claim 13 wherein said step of providing a base structure includes providing an electrically conductive base structure defining a plurality of spaced-apart charged particle emission sites, each of which includes one or more of said emitting tips integral with said base structure; wherein said step of providing a control electrode structure at said site includes providing such a structure for each of said sites; and said step of controlling the potential field pattern in said spatial volume includes selecting a desired electromagnetic interaction between said base and control electrode structure at and adjacent said plurality of sites during the extraction of particles from the same. 
     
     
       15. The method of claim 14 wherein said step of providing an electrically conductive control electrode structure for each of said sites includes providing a common control electrode for said sites having generally annular sections, each of which circumscribes an associated one of said sites, and generally linear connection sections providing conductive paths connecting said plurality of annular sections. 
     
     
       16. The method of claim 14 wherein said step of controlling the potential field pattern which will interact with electrically charged particles produced at each of said sites includes maintaining said base substantially free of shielding by said control electrode structure in the regions between said spaced-apart sites. 
     
     
       17. The method of any of the previous claims 10 through 16 wherein each of said spaced-apart particle emission sites are electron emission sites. 
     
     
       18. A method of constructing a particle field emission structure which comprises the steps of: A. applying a layer of insulating material on one surface of a base structure;   B. applying a generally continuous and planar layer of electrically conductive material on said insulating material with a plurality of spaced-apart apertures through said layers;   C. forming electrically charged particle emission sites at said apertures; and thereafter   D. removing substantially all of said layer of electrically conductive material between said sites to form a control electrode structure for electromagnetic interaction with said base structure to extract particles from said emission sites while enabling potential on said base structure to aid the formation of a potential field pattern in the spatial volume on the side of said control electrode structure opposite said base structure which will provide desired trajectories therethrough of particles formed at said sites.   
     
     
       19. The method of claim 18 of constructing a field emission cathode wherein said step of removing includes leaving between said sites, lead sections of said electrically conductive material to provide the electrically conductive paths necessary for common energization of a plurality of said sites. 
     
     
       20. The method of claim 18 wherein said step of removing substantially all of said layer of electrically conductive material includes etching said material from said insulating material in a preselected pattern. 
     
     
       21. The method of claim 1 wherein said insulating material is applied as a layer on said surface of said base structure, and further including the step of removing substantially all of said layer of insulating material between said particle emission sites.